A mechanism for accelerating and decelerating a vehicle during driving consists of pedal systems such as an accelerator pedal and brake pedal for use by the driver to operate the vehicle and a vehicle output system including an engine throttle and brake calipers which serve as a means of changing vehicle motion. Conventionally, the pedal systems and vehicle output system are connected mechanically, and consequently operation of the pedal systems results directly in operation of the vehicle output system. Thus, driver's actions equal vehicle behavior. However, recent advances in electronic-control technologies and by-wire technologies have made it possible to connect the pedal systems and vehicle output system via electric communications, and thereby made it possible to control the operation of the pedal systems and operation of the vehicle output system separately. By installing actuators on the pedal systems and changing pedal position and pedal reaction force according to circumstances, the by-wire technologies make it possible to enhance the safety of driving, provide various types of feel, improve drivability, and reduce driver fatigue. For example, JP-A-2002-323930 discloses a technique for reducing driver fatigue by adjusting the pedal reaction force according to circumstances.
It takes electric power to drive a pedal system equipped with an actuator. Also, an input processor is needed to control the actuator. Besides, the input processor itself consumes power. Consequently, the pedal system equipped with an actuator needs consideration to electrical conditions, which are not needed for the pedal system connected mechanically with a vehicle output system. Techniques needed for that include, for example, a technique for reducing power consumption by cutting off power when there is no need to operate the pedal system such as when the vehicle is stopped, technique for activating and deactivating the pedal system by controlling the power to the pedal system and vehicle output system, and technique for controlling the pedal position when activating and deactivating the pedal system.